Mitigating Earthquake Pounding of Adjacent Buildings

During strong earthquakes, buildings sway. If these buildings are adjacent and have insufficient space between them, the sway will bring about multiple collisions. These collisions can cause structural damage and possible building collapse. These collisions are referred to as structural pounding. This pounding is a function of the strength and depth of the earthquake, distance from the earthquake epicentre and geology of the building site. To investigate potential pounding mitigation, historic data from previous earthquakes is used as a guide. The data is only partially relevant because each earthquake event has its own unique features. Taking this into account, an active feedback system; made up of a brake and stepper motor, was designed to investigate pounding mitigation. The design focuses on the presence of adjacent buildings and their proximity. The experiments performed have shown that an active system is viable, and that pounding can be reduced. Building accelerations are comparable with those recorded in full-sized buildings, albeit marginally higher due to model flexibility. Earthquake amplification through the building is within acceptable standards and deceleration spikes have been controlled by a deceleration mechanism. The deceleration mechanism is to reduce the braking spikes during feedback control. The measured power requirements of the model were compared with calculated power requirements with the aid of distance-measuring lasers and an analytical method using the equations of motion. (E.O.M). The laser measuring power was within 0.2%, and the E.O.M. within 0.9% of the measured power. These figures are acceptable considering the assumptions upon which the study is based. A real-size analysis of the power requirements for three- and four- storey buildings was calculated. The calculation was based on the model analysis. The analysis showed that a large peak of electrical power is required for the active system during braking and motor movements. The calculated power requirement is in the vicinity 46kW, this figure is high but not insurmountable considering such powers being used in the automotive industry. This large power requirement can be distributed across the building using two or more systems, which also reduces the stress on the building. Since the energy requirements are high, the total power for the active system is minimal because of the active time of the earthquake. The power and peak requirements are the specifications needed for designing the active system. A parametric study on changes in building natural frequency and distance apart, has shown a linear relationship with possible power changes of up to 2.8%. To obtain more accurate results further studies are required. Such studies will need to use scaled models and a more substantial shake table. These improvements will allow for fewer assumptions and more accurate results.